JP2020029231A - Travelling support device - Google Patents

Abstract

To provide a travelling support device that can previously acquire a state of a road surface in a travelling direction of a vehicle.SOLUTION: The travelling support device comprises, for example: a sound wave control part that transfers sound waves toward a travelling direction of a vehicle and acquires information about reflected waves from a ranging part that receives the reflected waves reflected from an object; an information acquiring part that acquires information about temperatures around the vehicle; and a determining part that determines that a road surface in the travelling direction of the vehicle is a frozen road surface when determining that the ranging part has received reflected waves with signal strength of a prescribed value or more from a predetermined distance on the basis of the information about the reflected waves, if a temperature based on the temperature information is less than a prescribed temperature.SELECTED DRAWING: Figure 4

Description

  An embodiment of the present invention relates to a driving support device.

  Conventionally, by using various sensors mounted on a vehicle, an object existing around the vehicle, for example, another vehicle, a building, a tree, a pedestrian, or the like that can be an obstacle is detected, and contact with the object is performed. There have been proposed various techniques for performing braking support to avoid such a situation. In such a device, a sensor different from a sensor that detects an object estimates a road surface condition (a coefficient of road surface friction) and adjusts a braking force, thereby realizing contact avoidance with an object according to a situation. I have.

JP-A-5-310110 Japanese Patent No. 4966736

  The road surface friction coefficient is a ratio of a friction force acting on a contact surface between a vehicle wheel and a road surface and a pressure acting perpendicular to the contact surface. Therefore, the road surface friction coefficient cannot be estimated unless the wheels have reached the position of the road surface to be estimated. However, for example, when the road surface ahead in the traveling direction of the vehicle is frozen, the road surface friction coefficient at the time of braking is smaller than the current road surface friction coefficient, and a control delay may occur because the stopping distance is assumed to be short. is there. Therefore, if a travel support device capable of acquiring (or estimating) the road surface state in the traveling direction of the vehicle in advance can be provided, control delays and the like can be reduced or suppressed, which is significant.

  The traveling support device according to the embodiment is, for example, a sound wave control unit that transmits a sound wave in the traveling direction of the vehicle and acquires information on the reflected wave from a distance measuring unit that receives a reflected wave reflected from an object. An information acquisition unit for acquiring temperature information around the vehicle; and a signal intensity from a predetermined distance or more to a predetermined value or more based on the reflected wave information when the temperature based on the temperature information is lower than a predetermined temperature. And a determining unit that determines that the road surface in the traveling direction of the vehicle is a frozen road surface when the distance measuring unit determines that the reflected wave has been received. According to this configuration, for example, when the road surface is frozen at a temperature lower than the predetermined temperature, when an object reflecting the sound wave transmitted in the traveling direction of the vehicle exists, a part of the transmitted sound wave is It is more likely that the light will be reflected back. In other words, the distance measuring unit is more likely to obtain a strong reflected wave from a position farther than a reflected wave obtained when the road surface is not frozen. In this case, by determining that the road surface in the traveling direction of the vehicle is a frozen road surface, the road surface state (freezing state) at a position distant in the traveling direction of the vehicle can be acquired (estimated) in advance.

  The traveling support device according to the embodiment, for example, when it is determined that the frozen road surface, the vehicle traveling toward an object existing in the traveling direction of the vehicle that reflected the sound wave, the vehicle and the object contact. The vehicle may further include a control unit that executes the braking control from a position of a second braking distance longer than the first braking distance when the road surface is not frozen, which can be avoided. According to this configuration, for example, when it is determined that a frozen road surface exists at a position separated in the traveling direction of the vehicle, a second braking distance farther than the first braking distance for avoiding contact with an object while traveling on a non-freezing road surface is determined. Since the braking is started from the position of the braking distance, the contact avoidance braking with the object in consideration of the slip of the wheel on the frozen road surface can be realized.

  The sound wave control unit of the driving support device according to the embodiment may acquire the information of the reflected wave from, for example, the distance measuring unit provided so as to be able to transmit waves substantially parallel to the traveling direction of the vehicle. . According to this configuration, for example, it is possible to reduce the possibility that the transmitted sound wave is mainly directed to the road surface and is excessively reflected on the road surface. As a result, in the case of a non-freezing road surface, a strong reflected wave is acquired from the road surface, and erroneous determination of determining as a frozen road surface can be reduced. Further, in the case of a non-freezing road surface, erroneous detection of a road surface or a small object on the road surface as an obstacle can be suppressed.

  The determination unit of the traveling support device according to the embodiment determines that the road surface is the frozen road surface, for example, when the frequency of receiving the reflected wave having the signal intensity equal to or higher than the predetermined value is equal to or higher than a predetermined number. There may be a threshold, and the determination threshold may be changed according to the speed of the vehicle at the time of the determination. When the speed of the vehicle transmitting the sound waves changes, the number of reflected waves received per unit period with respect to the transmitted sound waves changes. According to this configuration, for example, since the determination threshold is changed according to the speed of the vehicle, it is possible to reduce the variation in the determination accuracy due to the speed of the vehicle.

FIG. 1 is an exemplary perspective view showing a state in which a part of a vehicle compartment of a vehicle equipped with the driving support device of the embodiment is seen through. FIG. 2 is an exemplary plan view of a vehicle equipped with the driving support device of the embodiment. FIG. 3 is an exemplary block diagram of a configuration of a parking assistance system including the driving assistance device according to the embodiment. FIG. 4 is an exemplary block diagram of a configuration of the driving support device realized by the CPU of the driving support system of the embodiment. FIG. 5 is an exemplary schematic diagram illustrating a positional relationship between a vehicle equipped with the driving assistance device of the embodiment and a target object existing in a traveling direction and a state of transmission and reception of ultrasonic waves. FIG. 6 is a graph exemplarily showing a reception tendency of a reflected wave received when a vehicle equipped with the driving support device of the embodiment approaches a target object in a scene where there is no frozen road surface (snow road surface). is there. FIG. 7 exemplarily shows a reception tendency of a reflected wave received when a vehicle equipped with the driving support device of the embodiment approaches a target object in a scene where there is no frozen road surface (non-freezing asphalt road surface). It is a graph shown. FIG. 8 is a graph exemplarily showing a receiving tendency of a reflected wave received when a vehicle equipped with the driving support device of the embodiment approaches a target object in a scene where a frozen road surface exists. FIG. 9 is a table exemplarily showing the state of transmission and reception of ultrasonic waves when the traveling support device of the embodiment classifies scenes based on whether or not the road surface is frozen and whether or not the target object is present. FIG. 10 is a map exemplarily showing a relationship between a determination threshold value serving as a reference when determining whether or not a frozen road surface is present and the vehicle speed in the driving support device of the embodiment. FIG. 11 is an exemplary flowchart illustrating a flow of a frozen road surface determination and a brake control process performed by the driving support device of the embodiment.

  Hereinafter, exemplary embodiments of the present invention will be disclosed. The configurations of the embodiments described below, and the operations, results, and effects provided by the configurations are examples. The present invention can be realized by configurations other than those disclosed in the following embodiments, and can obtain at least one of various effects based on the basic configuration and derivative effects. .

  In the present embodiment, the vehicle 1 equipped with the driving support device may be, for example, an automobile using an internal combustion engine (not shown) as a driving source, that is, an internal combustion engine automobile, or an automobile using an electric motor (not shown) as a driving source. That is, it may be an electric vehicle, a fuel cell vehicle, or the like, a hybrid vehicle using both of them as driving sources, or a vehicle equipped with another driving source. Further, the vehicle 1 can be mounted with various transmissions, and can be mounted with various devices required for driving the internal combustion engine and the electric motor, such as systems and components. Further, the type, number, layout, and the like of the devices related to the driving of the wheels 3 in the vehicle 1 can be variously set.

  As illustrated in FIG. 1, the vehicle body 2 constitutes a vehicle compartment 2 a in which a passenger (not shown) rides. A steering unit 4, an acceleration operation unit 5, a braking operation unit 6, a shift operation unit 7, and the like are provided in the vehicle interior 2a in a state of facing a driver's seat 2b as an occupant. The steering unit 4 is, for example, a steering wheel protruding from the dashboard 25, the acceleration operation unit 5 is, for example, an accelerator pedal located below the driver's feet, and the braking operation unit 6 is, for example, a driver's The shift pedal 7 is, for example, a shift lever projecting from the center console. The steering unit 4, the acceleration operation unit 5, the braking operation unit 6, the shift operation unit 7, and the like are not limited to these.

  Further, a display device 8 as a display output unit and an audio output device 9 as an audio output unit are provided in the passenger compartment 2a. The display device 8 is, for example, an LCD (liquid crystal display), an OELD (organic electroluminescent display), or the like. The audio output device 9 is, for example, a speaker. The display device 8 is covered with, for example, a transparent operation input unit 10 such as a touch panel. The occupant can visually recognize an image displayed on the display screen of the display device 8 via the operation input unit 10. Further, the occupant can execute the operation input by operating the operation input unit 10 by touching, pushing, or moving the operation input unit 10 with a finger or the like at a position corresponding to the image displayed on the display screen of the display device 8. . The display device 8, the audio output device 9, the operation input unit 10, and the like are provided, for example, on the monitor device 11 located at the center of the dashboard 25 in the vehicle width direction, that is, in the left-right direction. The monitor device 11 can include an operation input unit (not shown) such as a switch, a dial, a joystick, and a push button. An audio output device (not shown) can be provided at another position in the passenger compartment 2a different from the monitor device 11, and audio is output from the audio output device 9 of the monitor device 11 and another audio output device. be able to. Note that the monitor device 11 can also be used, for example, as a navigation system or an audio system.

  Further, a display device 12 (see FIG. 3) different from the display device 8 is provided in the passenger compartment 2a. The display device 12 is provided, for example, on an instrument panel 26 (see FIG. 1) of the dashboard 25, and is located substantially at the center of the instrument panel 26, between the speed display unit and the rotation speed display unit. The screen size of the display device 12 is smaller than the screen size of the display device 8. On the display device 12, an image mainly indicating information related to the driving support of the vehicle 1 can be displayed. The amount of information displayed on the display device 12 may be smaller than the amount of information displayed on the display device 8. The display device 12 is, for example, an LCD, an OELD, or the like. The information displayed on the display device 12 may be displayed on the display device 8.

  Further, as exemplified in FIGS. 1 and 2, the vehicle 1 is, for example, a four-wheeled vehicle, and has two left and right front wheels 3F and two left and right rear wheels 3R. Each of these four wheels 3 can be configured to be steerable. As illustrated in FIG. 3, the vehicle 1 has a steering system 13 that steers at least two wheels 3. The steering system 13 has an actuator 13a and a torque sensor 13b. The steering system 13 is electrically controlled by an ECU 14 (electronic control unit) or the like to operate the actuator 13a. The steering system 13 is, for example, an electric power steering system, an SBW (steer by wire) system, or the like. The steering system 13 supplements the steering force by adding a torque, that is, an assist torque, to the steering unit 4 by the actuator 13a, or turns the wheels 3 by the actuator 13a. In this case, the actuator 13a may steer one wheel 3 or steer a plurality of wheels 3. Further, the torque sensor 13b detects, for example, a torque given to the steering unit 4 by the driver.

  As illustrated in FIGS. 1 and 2, an imaging unit 15 is provided on a wall below the rear trunk door 2h, which is the rear end 2e of the vehicle body 2, for example. The imaging unit 15 is, for example, a digital camera having a built-in imaging device such as a charge coupled device (CCD) or a CMOS image sensor (CIS). The imaging unit 15 can output moving image data at a predetermined frame rate. Each of the imaging units 15 has a wide-angle lens or a fisheye lens, and can capture, for example, a range of 140 ° to 220 ° in the horizontal direction. The optical axis of the imaging unit 15 is set obliquely downward. Therefore, the imaging unit 15 sequentially captures rear images around the rear of the vehicle body 2 including a movable road surface behind the vehicle 1 and an area where the vehicle 1 can park, and outputs the captured images as captured image data. Note that in other embodiments, a plurality of imaging units 15 may be provided. For example, a front image of the vehicle 1 may be acquired by being provided on the front side of the vehicle body 2, that is, on the front side in the vehicle front-rear direction. Further, the imaging unit 15 may be provided, for example, on the left and right door mirrors of the right end and the left end of the vehicle body 2 to acquire left and right side images of the vehicle 1. When the imaging unit 15 is provided at the rear end of the vehicle body 2, for example, when the vehicle 1 moves backward, it is possible to provide a rear image through the display device 8 for confirming the safety of the rear. When the imaging unit 15 is provided at the front end or the side end of the vehicle body 2, images for confirming safety in each direction can be provided. The ECU 14 performs arithmetic processing and image processing based on the image data obtained by the plurality of imaging units 15 to generate an image with a wider viewing angle, or a virtual bird's-eye view of the vehicle 1 viewed from above. An image may be generated.

  As illustrated in FIGS. 1 and 2, the vehicle body 2 includes, for example, four distance measuring units 16 a to 16 d and eight distance measuring units 17 a to 17 h as a plurality of distance measuring units 16 and 17. Is provided. The distance measuring units 16 and 17 are sonars that emit, for example, an ultrasonic wave and capture a reflected wave as an example of a sound wave. Sonar can also be called a sonar sensor or an ultrasonic detector. The ECU 14 can measure the presence or absence of an object such as an obstacle located around the vehicle 1 and the distance to the object based on the detection results of the distance measurement units 16 and 17. The distance measuring unit 17 can be used, for example, to detect a relatively short distance object, and the distance measuring unit 16 can be used, for example, to detect a relatively long distance object farther than the distance measuring unit 17. The distance measuring unit 17 can be used, for example, for detecting objects in front and behind the vehicle 1, and the distance measuring unit 16 can be used for detecting an object on the side of the vehicle 1.

  Furthermore, in the case of the present embodiment, for example, the distance measuring unit 17 can also be used as a sensor that acquires information for determining whether or not the road surface in the traveling direction of the vehicle 1 is a frozen road surface. In the case of a frozen road surface, the surface irregularities of the road surface may become smoother than a non-freezing road surface due to freezing, and the reflectivity (echo) of the ultrasonic wave may be improved. Also, since sound waves including ultrasonic waves propagate in the air, the lower the temperature, the smaller the loss during propagation. The traveling support device of the present embodiment makes use of this difference in characteristics to determine the presence or absence of a frozen road surface. The details of the determination of the presence or absence of a frozen road surface will be described later.

  As illustrated in FIG. 3, in the driving support system 100, in addition to the ECU 14, the monitor device 11, the steering system 13, the distance measurement units 16 and 17, a brake system 18, a steering angle sensor 19, an accelerator sensor 20 , A drive system 21, a wheel speed sensor 22, a shift sensor 23, etc., are electrically connected via an in-vehicle network 24 as an electric communication line. The in-vehicle network 24 is configured as, for example, a CAN (controller area network). The ECU 14 can control the steering system 13, the brake system 18, the drive system 21 and the like by sending a control signal through the in-vehicle network 24. Further, the ECU 14 detects detection results of the torque sensor 13b, the brake sensor 18b, the steering angle sensor 19, the distance measuring units 16, 17, the accelerator sensor 20, the shift sensor 23, the wheel speed sensor 22, and the like via the in-vehicle network 24, An operation signal or the like of the operation input unit 10 or the like can be received.

  The ECU 14 includes, for example, a CPU 14a (central processing unit), a ROM 14b (read only memory), a RAM 14c (random access memory), a display control unit 14d, a voice control unit 14e, an SSD 14f (solid state drive, flash memory), and the like. ing. The CPU 14a, for example, performs image processing related to images displayed on the display devices 8 and 12, determines the presence or absence of a frozen road surface in the traveling direction of the vehicle 1 when performing driving support, and controls contact avoidance according to the road surface state ( Various arithmetic processes and controls, such as braking control, etc., and an alarm output when a frozen road surface is found, can be executed.

  The CPU 14a reads a program installed and stored in a non-volatile storage device such as the ROM 14b, and can execute arithmetic processing according to the program. The RAM 14c temporarily stores various data used in the calculation by the CPU 14a. In addition, the display control unit 14d mainly performs image processing using image data obtained by the imaging unit 15 and synthesis of image data displayed on the display device 8 among arithmetic processing in the ECU 14. In addition, the voice control unit 14 e mainly performs processing of voice data output from the voice output device 9 in the arithmetic processing in the ECU 14. The SSD 14f is a rewritable nonvolatile storage unit, and can store data even when the power of the ECU 14 is turned off. Note that the CPU 14a, the ROM 14b, the RAM 14c, and the like can be integrated in the same package. Further, the ECU 14 may be configured to use another logical operation processor, a logical circuit, or the like, such as a DSP (digital signal processor), instead of the CPU 14a. Further, a hard disk drive (HDD) may be provided instead of the SSD 14f, and the SSD 14f and the HDD may be provided separately from the ECU 14.

  The brake system 18 includes, for example, an anti-lock brake system (ABS) that suppresses lock of the brake, an electronic stability control (ESC) that suppresses a side slip of the vehicle 1 at the time of cornering, and increases the braking force ( Electric brake system for executing brake assist), BBW (brake by wire) and the like. The brake system 18 applies a braking force to the wheels 3 and thus to the vehicle 1 via the actuator 18a. In addition, the brake system 18 can execute various controls by detecting a lock of a brake, an idling of the wheel 3, a sign of a skid, or the like based on a rotation difference between the left and right wheels 3 and the like. The brake sensor 18b is, for example, a sensor that detects the position of the movable part of the braking operation unit 6. The brake sensor 18b can detect the position of a brake pedal as a movable part.

  The steering angle sensor 19 is, for example, a sensor that detects a steering amount of the steering unit 4 such as a steering wheel. The steering angle sensor 19 is configured using, for example, a Hall element. The ECU 14 obtains, from the steering angle sensor 19, the amount of steering of the steering unit 4 by the driver, the amount of steering of each wheel 3 during automatic steering, and executes various controls. The steering angle sensor 19 detects a rotation angle of a rotating part included in the steering section 4. The steering angle sensor 19 is an example of an angle sensor.

  The accelerator sensor 20 is, for example, a sensor that detects the position of the movable part of the acceleration operation unit 5. The accelerator sensor 20 can detect the position of an accelerator pedal as a movable part. The accelerator sensor 20 includes a displacement sensor.

  The drive system 21 is an internal combustion engine (motor) system or a motor system as a drive source. The drive system 21 controls the fuel injection amount and intake air amount of the engine and the output value of the motor according to the required operation amount (for example, the depression amount of an accelerator pedal) of the driver (user) detected by the accelerator sensor 20. . Further, regardless of the operation of the user, the output values of the engine and the motor can be controlled in cooperation with the control of the steering system 13 and the brake system 18 according to the running state of the vehicle 1.

  The wheel speed sensor 22 is a sensor provided on each wheel 3 for detecting the amount of rotation of each wheel 3 and the number of rotations per unit time, and outputs a wheel speed pulse number indicating the detected number of rotations as a detection value. The wheel speed sensor 22 can be configured using, for example, a Hall element. The CPU 14a calculates a vehicle speed, a moving amount, and the like of the vehicle 1 based on the detection value acquired from the wheel speed sensor 22, and executes various controls. When calculating the vehicle speed of the vehicle 1 based on the detected value of the wheel speed sensor 22 of each wheel 3, the CPU 14a determines the vehicle speed of the vehicle 1 based on the speed of the wheel 3 having the smallest detected value among the four wheels. Execute control. In addition, when there is a wheel 3 having a larger detection value than the other wheels 3 among the four wheels, the CPU 14a determines, for example, that the number of rotations in a unit period (unit time or unit distance) is larger than that of the other wheels 3. When there are more wheels 3 than a predetermined number, the wheels 3 are regarded as being in a slip state (idling state), and various controls are executed. The wheel speed sensor 22 may be provided in the brake system 18 in some cases. In that case, the CPU 14a acquires the detection result of the wheel speed sensor 22 via the brake system 18.

  The shift sensor 23 is, for example, a sensor that detects the position of a movable part of the speed change operation unit 7. The shift sensor 23 can detect the position of a lever, arm, button, or the like as a movable part. The shift sensor 23 may include a displacement sensor or may be configured as a switch.

  The configuration, arrangement, electrical connection form, and the like of the various sensors and actuators described above are merely examples, and can be set (changed) in various ways.

  FIG. 4 is an exemplary block diagram of a configuration of the driving support device 28 realized by the CPU 14a of the driving support system 100 according to the embodiment. The CPU 14a includes various modules that are implemented as the driving support device 28 by reading a program installed and stored in a storage device such as the ROM 14b and executing the program. The driving support device 28 realized by the CPU 14a includes, for example, a sound wave control unit 30, an information acquisition unit 32, a vehicle speed calculation unit 34, a threshold value determination unit 36, a determination unit 38, a distance calculation unit 40, a deceleration start position calculation unit 42, and a brake. A control unit 44, an alarm processing unit 46 and the like are provided.

  The sound wave control unit 30 includes a wave transmission control unit 30a and a wave reception control unit 30b. In the case of the present embodiment, in order to determine the presence / absence of a frozen road surface in the traveling direction of the vehicle 1, the distance measuring unit 17 in which the sound wave transmission direction is the traveling direction of the vehicle 1 can be used. Conventionally, the presence or absence of a frozen road surface is determined by using a distance measuring unit 17 provided for detecting an object existing around the vehicle 1, so that a new additional function can be performed without an increase in parts cost and the like. Can be realized. FIG. 5 is a schematic diagram illustrating a case where the presence or absence of a frozen road surface is determined using the distance measuring units 17 (17a to 17d) provided behind the vehicle 1 when the vehicle 1 travels backward on the road surface 48. As described above, the distance measurement unit 17 uses an ultrasonic sonar as an example. The distance measuring unit 17 includes an ultrasonic vibrator (not shown). The transmission control unit 30a outputs a drive signal for vibrating the ultrasonic transducer of the distance measuring unit 17 at a constant period, and transmits the ultrasonic wave W from the vibration surface of the distance measuring unit 17. The ultrasonic wave W propagates in the medium (in the case of the present embodiment, in the air) while spreading in a conical shape around the ultrasonic transducer as the sound source. The distance measuring unit 17 is in a state where the ultrasonic wave W transmitted under the control of the transmission control unit 30a is reflected on the target object 50, which is present around the vehicle 1, for example, and is reflected by the target object 50. To receive waves. The reception controller 30b acquires the superposed signals as reception signals. When the ultrasonic wave W propagates in the air under a normal environment, the ultrasonic wave W is attenuated as the propagation distance increases. Therefore, as the target object 50 that reflects the ultrasonic wave W is farther from the distance measuring unit 17, the signal intensity that can be acquired by the wave receiving control unit 30b becomes lower. Note that the “normal environment” in this case is an environment in which reflection of the ultrasonic wave W is unlikely to occur except for the target object 50, for example, the road surface 48 on which the vehicle 1 (the distance measuring unit 17) exists is not in a flat hard state. Is the case. A general road surface 48, such as a paved road surface (asphalt road surface), an unpaved road surface, a snowy road surface, or the like, has fine irregularities on its surface, and reflects or absorbs the ultrasonic waves W irregularly. As a result, the ultrasonic wave W is mainly reflected by the target object 50, and the presence or absence and the position of the target object 50 can be detected. The ultrasonic wave W transmitted from the distance measuring unit 17 is set to be transmitted, for example, substantially in parallel with the traveling direction of the vehicle 1. In other words, the distance can be measured by the ultrasonic wave W transmitted from the distance measuring unit 17 to a greater distance in the traveling direction of the vehicle, and the road surface 48 and small objects existing on the road surface 48 are mainly directed to the road surface 48. In this way, excessive reflection is suppressed, and erroneous detection of the road surface 48 and small objects as obstacles is suppressed.

  By the way, when the road surface 48 in the traveling direction of the vehicle 1 is frozen, the distance measuring unit 17 may be able to receive a strong reflected wave from a position far from the vehicle 1 (the distance measuring unit 17). For example, when the road surface 48 freezes, fine irregularities on the surface of the road surface 48 are covered with ice, and the road surface 48 is in a state close to a smooth hard plane. As a result, when the ultrasonic wave W transmitted from the distance measuring unit 17 hits the frozen road surface 48, the ultrasonic wave W advances in the traveling direction of the vehicle 1 (behind the vehicle 1) without being irregularly reflected, and the target object 50 existing there is present. Hit. That is, the direct wave transmitted from the distance measuring unit 17 and the indirect wave once reflected on the frozen road surface 48 are reflected by the target object 50, and the superimposed result is received by the distance measuring unit 17. On the other hand, when the road surface 48 is not frozen, the ultrasonic waves hitting the road surface 48 are irregularly reflected due to fine irregularities on the surface of the road surface 48, and the indirect waves toward the target object 50 are reduced as compared with the case of the frozen road surface. As a result, when the road surface 48 is frozen, the reception intensity (signal intensity) of the reflected wave from a position distant from the distance measuring unit 17 is higher than when the road surface 48 is not frozen.

  When the road surface 48 freezes, the temperature (air temperature) around the road surface 48, that is, around the vehicle 1 is lower than when the road surface 48 is not frozen. The easiness of propagation of a sound wave (ultrasonic wave W) is generally affected by the attenuation at the time of propagation determined by the temperature and humidity of a medium (in this case, air). Thus, the lower the temperature, the smaller the attenuation. Therefore, in an environment where the road surface 48 is frozen (low-temperature environment), the ultrasonic wave W reflected at a position distant from the distance measuring unit 17 propagates with little attenuation. That is, when there is a possibility that the road surface 48 is frozen, the distance measuring unit 17 (the wave receiving control unit 30b) acquires a reflected wave with a strong received wave intensity (signal strength) from a position farther than when the road surface 48 is not frozen. be able to.

  In FIG. 5, it is known that the reception intensity (signal intensity) of the reflected wave from near the contact position P between the road surface 48 and the target object 50 is high. This is because the superposition of the ultrasonic waves W around the contact position P occurs more strongly than other parts, for example, a position far from the contact position P (a position far from the road surface 48) in the target object 50. Further, when the road surface 48 is frozen, the attenuation at the time of propagation of the ultrasonic wave W is small as described above, and the reception intensity (signal intensity) of the reflected wave from the vicinity of the contact position P increases. In addition, the superimposition effect of the ultrasonic waves W (indirect waves) reflected on the road surface 48 near the contact position P is added, and the reception intensity (signal intensity) of the reflected wave from the vicinity of the contact position P is further increased.

  FIGS. 6 to 8 show the peak value (the intensity of the reflected wave) and the detection distance (the target object) based on the reception intensity (signal intensity) acquired by the reception control unit 30b when the state of the road surface 48 is changed. It is an exemplary graph showing the relationship (wave receiving tendency) of the distance up to 50. A plot point in the graph is a signal intensity (peak value) when a reflected wave with respect to the ultrasonic wave W transmitted by the distance measuring unit 17 is received at a certain timing. For example, the transmission of the ultrasonic wave W is as follows. It is performed five times per second. Further, the range of recognition of the target object 50 under the normal environment of the distance measuring unit 17 (under the environment of a non-freezing road surface) is, for example, within 3000 mm from the distance measuring unit 17. If the target object 50 exists within 3000 mm, it is assumed that a reflected wave having a high signal intensity (high peak value) can be stably acquired, and the existence of the target object 50 and the distance to the target object 50 can be recognized. Note that even when the distance is 3000 mm or more, the wave reception control unit 30b can acquire data indicating that some object exists, although the distance accuracy is reduced.

  FIG. 6 shows a wave receiving tendency acquired by the wave receiving control unit 30b when the road surface 48 is a non-freezing asphalt road surface. The temperature around the vehicle 1 is, for example, 10 ° C., which does not lead to road surface freezing. As shown in FIG. 6, when the vehicle 1 (the distance measuring unit 17) approaches the target object 50, when the relative distance between the vehicle 1 (the distance measuring unit 17) and the target object 50 is, for example, within 3000 mm, the target A strong reflected wave reflected by the object 50 can be received, and a signal having a high received wave intensity (high peak value) can be obtained. That is, in an environment where the road surface 48 is not frozen, the reception control unit 30b determines the presence or absence of the target object 50 based on the signal intensity, and determines the target object 50 based on the time from transmission to reception and the sound speed at the time of measurement. It is possible to obtain information from which 50 existing positions (relative distances) can be calculated. A plurality of distance measuring units 17 (17a to 17d) are arranged at the rear of the vehicle 1, and transmit and receive ultrasonic waves W to and from the rear area of the vehicle 1 in the same manner. Therefore, by using the detection results of at least two distance measuring units 17, triangulation can be performed, and more accurate position detection of the target object 50 can be performed.

  On the other hand, as described above, when the relative distance between the vehicle 1 (the distance measuring unit 17) and the target object 50 becomes 3000 mm or more, which is the recognition range of the distance measuring unit 17, the reflected wave acquired by the wave receiving control unit 30b is obtained. The signal strength decreases due to attenuation during propagation of the ultrasonic wave W. That is, the wave receiving control unit 30b can obtain a wave receiving tendency in which the target object 50 that has entered the recognition range of the distance measuring unit 17 can be identified.

  FIG. 7 shows a wave receiving tendency acquired by the wave receiving control unit 30b when the road surface 48 is a frozen road surface. In addition, in the case of FIG. 7, the road surface 48 is formed of the same asphalt road surface as the case of FIG. 6, after snow or frost has accumulated, or after rain, and water or rainwater after the snow or frost has once melted. Is frozen on the asphalt surface. For example, a state called “ice burn” is also included. Further, the temperature around the vehicle 1 is, for example, “0 ° C.” or less, for example, −10 ° C., which leads to road surface freezing.

  As shown in FIG. 7, when the road surface 48 is a frozen road surface, similarly to the case of the non-freezing road surface in FIG. 6, when the vehicle 1 (the distance measuring unit 17) approaches the target object 50, the vehicle 1 ( When the relative distance between the distance measuring unit 17) and the target object 50 is, for example, 3000 mm or less, a strong reflected wave reflected by the target object 50 can be received, and a signal having a high reception intensity (high peak value) is obtained. Can be That is, the reception control unit 30b determines whether or not the target object 50 is present based on the signal intensity, regardless of whether or not the road surface 48 is frozen, and determines whether the target object 50 is present based on the time from transmission to reception and the sound speed at the time of measurement. Information from which the existence position (relative distance) can be calculated can be obtained. Also in this case, more accurate position detection of the target object 50 can be performed by triangulation using the plurality of distance measurement units 17 (17a to 17d).

  When the target object 50 exists in the traveling direction of the vehicle 1 and the road surface 48 is a frozen road surface, as described above, the attenuation amount of the ultrasonic wave W due to the decrease in the temperature of the medium decreases, and after the ultrasonic wave W is reflected on the frozen road surface. The superposition of indirectly reflected waves reflected by the target object 50 occurs simultaneously. As a result, the wave reception control unit 30b can receive a strong reflected wave even from the target object 50 located at a distant position where only a low (weak) peak value that cannot be normally distinguished from the noise of the road surface 48 can be obtained. Thus, it is possible to obtain a reception tendency such that a signal having a high reception intensity (a high peak value) is obtained. For example, as shown in FIG. 7, in FIG. 6, a reflected wave having a high peak value is obtained in a region E at a detection distance of, for example, 3000 mm or more where a reflected wave having a high peak value was not obtained. In other words, when the traveling support device 28 determines that the distance measuring unit 17 has received a reflected wave having a signal strength equal to or greater than a predetermined value from a predetermined distance or more based on information of the reflected wave when the temperature is lower than the predetermined temperature. In addition, it can be determined that the road surface in the traveling direction of the vehicle 1 may be a frozen road surface. In this case, the reflected waves are merely superimposed and the signal intensity is merely increased. Therefore, the presence or absence of the target object 50 based on the signal intensity and the calculation of the position (relative distance) of the target object 50 based on the time from transmission to reception and the sound speed at the time of measurement are determined for the reflected wave from the distant position. It is also data indicating possible information. In addition, more accurate position detection of the target object 50 can be performed by triangulation using the plurality of distance measurement units 17 (17a to 17d).

  FIG. 8 shows a wave reception tendency acquired by the wave reception control unit 30b when the road surface 48 is a non-freezing snowy road surface. The road surface μ when the vehicle 1 travels differs between a snowy road surface and a frozen road surface. In particular, since the braking characteristics of the vehicle 1 at low speed are different, it is necessary to distinguish between them. The temperature around the vehicle 1 is, for example, lower than 0 ° C., for example, −10 ° C., at which the snowy road surface is maintained. As in the case of FIGS. 6 and 7, when the vehicle 1 (the distance measuring unit 17) approaches the target object 50, the relative distance between the vehicle 1 (the distance measuring unit 17) and the target object 50 is, for example, within 3000 mm. In this case, a strong reflected wave reflected by the target object 50 can be received, and a signal having a high receiving intensity (high peak value) can be obtained. That is, the reception control unit 30b determines whether or not the target object 50 is present based on the signal intensity, regardless of whether or not the road surface 48 is frozen, and determines whether the target object 50 is present based on the time from transmission to reception and the sound speed at the time of measurement. Information from which the existence position (relative distance) can be calculated can be obtained. Also in this case, more accurate position detection of the target object 50 can be performed by triangulation using the plurality of distance measurement units 17 (17a to 17d).

  On the other hand, when the relative distance between the vehicle 1 (the distance measuring unit 17) and the target object 50 becomes, for example, 3000 mm or more, which is the recognition range of the distance measuring unit 17, the signal intensity of the reflected wave acquired by the wave receiving control unit 30b becomes It decreases due to attenuation during propagation of the ultrasonic wave W. Snow has the property of absorbing the vibration of sound waves. In addition, snow crystals tend to form fine irregularities on the snowfall surface. As a result, despite the low ambient temperature, the reflection of the ultrasonic wave W on the road surface 48 hardly occurs, and the possibility that the indirect wave reaches the target object 50 decreases. As a result, on a snowy road surface, similarly to a non-freezing asphalt road surface as shown in FIG. 6, the signal strength of a reflected wave from a long distance tends to be low.

  In FIGS. 6 to 8, in order to more efficiently and clearly determine the frozen road surface, for example, in a region where the peak value is low, it is difficult to distinguish the noise from noise, so that the region is filtered or excluded or distinguished. Thus, it may be determined whether or not a reflected wave having a signal strength equal to or more than a predetermined value is obtained from a predetermined distance or more.

  FIG. 9 is a table exemplarily showing the state of transmission and reception of ultrasonic waves when the scenes are different. As an example, scenes are classified according to the presence or absence of freezing of the road surface 48 and the presence or absence of the target object 50. When the road surface 48 is a frozen road surface and the target object 50 does not exist around the vehicle 1, the ultrasonic wave W transmitted from the distance measuring unit 17 is reflected on the frozen road surface, but the target object 50 does not exist. Do not return to the distance measuring unit 17 (vehicle 1) (the wave receiving control unit 30b does not acquire the signal of the reflected wave). The same applies to a case where the road surface 48 is a snowy road surface and the target object 50 is not present around the vehicle 1. In this case, since the possibility that the vehicle 1 comes into contact with an obstacle such as the target object 50 is low (no), the determination of whether or not the road surface 48 is frozen can be regarded as unnecessary in the braking control of the vehicle 1.

  When the road surface 48 is a frozen road surface and the target object 50 is present around the vehicle 1, the ultrasonic waves W transmitted from the distance measuring unit 17 are reflected on the frozen road surface and transmitted to the distance measuring unit 17 (vehicle 1). Return. FIG. 9 shows an example in which the ultrasonic wave W transmitted from the distance measuring unit 17 is reflected by the target object 50, and the reflected wave is further reflected on a frozen road surface (road surface 48) and returns to the distance measuring unit 17. Have been. In another example, the ultrasonic wave W transmitted from the distance measuring unit 17 is reflected on a frozen road surface (road surface 48), the reflected wave is further reflected on the target object 50, and is returned to the distance measuring unit 17 and received. In some cases. That is, the distance measuring unit 17 receives a strong reflected wave in which the direct wave not reflected on the frozen road surface (road surface 48) and the indirect wave reflected on the frozen road surface (road surface 48) are overlapped in the process of transmitting and receiving waves. Waves become possible. On the other hand, when the road surface 48 is a non-freezing road surface (snow road surface) and the target object 50 is present around the vehicle 1, the ultrasonic wave W transmitted from the distance measuring unit 17 is reflected by the target object 50. The reflected wave heading toward the snowy road surface (road surface 48) is irregularly reflected or absorbed on the snowy road surface, and is hard to return to the distance measuring unit 17 (vehicle 1). A part of the ultrasonic wave W transmitted from the distance measuring unit 17 goes to the snowy road surface (road surface 48). In this case, too, the indirect wave toward the target object 50 is irregularly reflected or absorbed on the snowy road surface, and very little. It is. Therefore, the distance measuring unit 17 mainly receives only direct waves that are not reflected on a frozen road surface (road surface 48) or the like, and the received wave intensity of the reflected wave is lower than when the road surface 48 is a frozen road surface. I do. In the case of a snowy road surface, the road surface friction coefficient is lower than that of a dry road surface. In this case, for example, by performing image processing or the like on the captured image data acquired by the imaging unit 15, it is possible to determine whether the road surface is a snowy road surface or a dry road surface. Therefore, in the case of a snowy road surface, the braking control can be performed using the result of the determination process different from the determination of the frozen road surface of the present embodiment.

  In the case of a non-freezing rainy road surface, since the rainwater does not cover the unevenness of the surface of the asphalt road surface, the ultrasonic wave W results in irregular reflection and the like, and shows the same wave receiving tendency as that of FIG. Further, even on an unpaved road surface, the ultrasonic waves W are irregularly reflected due to unevenness of the surface of the road surface, and show the same wave receiving tendency as that of FIG. Also in these situations, when the target object 50 does not exist in the traveling direction of the vehicle 1, the reception control unit 30b does not receive a remarkable reflected wave.

  Returning to FIG. 4, the information acquisition unit 32 acquires temperature information around the vehicle 1. For example, information from a temperature sensor for measuring the outside air temperature provided in the air conditioner of the vehicle 1 or a temperature sensor (a sensor for correcting the speed of sound based on temperature) provided in the distance measuring unit 16 or the distance measuring unit 17. Get the information of. In another embodiment, the temperature information of the position where the vehicle 1 exists, which is provided by an external information center, may be obtained using communication means such as the Internet or a telephone line. The method for acquiring the temperature information is not limited to these, and any method may be used as long as the temperature information around the vehicle 1 can be acquired. Further, a dedicated temperature sensor may be provided for determining the frozen road surface. In some cases, there is a difference between the outside air temperature and the road surface temperature. In such a case, the road surface temperature is estimated based on the acquired outside air temperature and the past data, and may be used as a determination condition (temperature threshold A described later) for determining the presence or absence of a frozen road surface, which contributes to more accurate determination. Can be.

  The vehicle speed calculation unit 34 calculates the vehicle speed of the vehicle 1 based on the detection result output from the wheel speed sensor 22. Further, the threshold value determination unit 36 determines a determination threshold value (a determination threshold value D described later) used when determining that the road surface 48 is a frozen road surface based on the vehicle speed of the vehicle 1 calculated by the vehicle speed calculation unit 34. The determination threshold can be determined in advance based on experiments or the like, and is stored in the ROM 14b or the like. The determination unit 38 determines whether or not the road surface 48 is a frozen road surface with reference to, for example, the wave reception tendency acquired by the wave reception control unit 30b. As described above, when the road surface 48 is a frozen road surface, in the region E (see FIG. 7) which is outside the recognition range of the distance measuring unit 17 and is a detection distance far from the distance measuring unit 17, the same region on the non-freezing road surface As compared with E (see FIG. 6), a plurality of signals having a stronger signal strength can be received. That is, the peak values of the plurality of reflected waves are plotted in the area E. The determination unit 38 compares, for example, the number of plots in the region E with the determination threshold (the number of determination plots) determined by the threshold determination unit 36, and when the number of plots is equal to or greater than the determination threshold, When the reception frequency of the reflected wave is equal to or more than a predetermined number, it is determined that the road surface in the traveling direction of the vehicle 1 is a frozen road surface.

  By the way, when the vehicle 1 is traveling and moving with respect to the target object 50, the unit period of the reflected wave reflected by the target object 50 among the ultrasonic waves W transmitted from the transmission control unit 30a at a predetermined cycle. The number of received waves changes according to the vehicle speed of the vehicle 1. For example, as shown in FIG. 10, as the vehicle speed of the vehicle 1 increases, the number of reflected waves that can be received per unit period (for example, one second), that is, the measurement plotted per unit period in FIGS. Fewer points. Therefore, the relationship between each vehicle speed (for example, every 1 km / h) of the vehicle 1 on the frozen road surface and the number of reflected waves that can be received (the number of plots) is acquired in advance. For example, when the vehicle speed is 5 km / h, and five or more reflected waves can be received in the area E, the determination unit 38 determines that the road surface 48 is a frozen road surface. In this case, the threshold value determination unit 36 determines the threshold value for the vehicle speed of 5 km / h as “5”.

  The distance calculation unit 40 determines the time from when the distance measuring unit 17 transmits the ultrasonic wave W until the ultrasonic wave W is reflected by the target object 50 and received by the distance measuring unit 17, and when the ultrasonic wave W is transmitted and received. The distance from the distance measuring unit 17 (vehicle 1) to the target object 50 is calculated based on the sound speed at the time of the wave (the sound speed corresponding to the temperature). As described above, the rear end 2e of the vehicle 1 is provided with a plurality (for example, four) of distance measuring units 17 (17a to 17d). These distance measuring units 17a to 17d can respectively transmit the ultrasonic wave W and receive the reflected wave to and from the target object 50 present behind the vehicle 1. In this case, the angle at which the same target object 50 faces differs depending on the position where the distance measuring unit 17 is arranged, and a difference occurs in the transmission / reception path. Therefore, the distance calculation unit 40 may calculate the position of the target object 50 more accurately by triangulation using the transmission and reception results of any two of the distance measurement units 17.

  The deceleration start position calculation unit 42 determines whether the road surface 48 is a non-freezing road surface based on the determination result of the determination unit 38, and performs the non-freezing operation when braking on the non-freezing road surface at the current vehicle speed of the vehicle 1. Calculate the required braking distance. Similarly, when it is determined that the road surface 48 is a frozen road surface based on the determination result of the determination unit 38, the deceleration start position calculation unit 42 determines whether or not to perform braking on the frozen road surface at the current vehicle speed of the vehicle 1. Calculate the required braking distance. Then, the deceleration start position calculation unit 42 refers to the distance to the target object 50 calculated by the distance calculation unit 40, and starts braking (deceleration) because the vehicle 1 can stop without contacting the target object 50. The "deceleration start position" to be calculated is calculated. The required braking distance during non-freezing and during freezing can be determined in advance for each vehicle speed by a test and stored in a storage unit such as the ROM 14b, for example, as a map. In addition, the required braking distance at the time of non-freezing may be set more finely according to the weather condition and the like, for example, for road surface drying, rainfall, snowfall, and the like.

  When it can be considered that the rear end 2e of the vehicle 1 has reached the deceleration start position calculated by the deceleration start position calculation unit 42, the braking control unit 44 automatically generates a braking force according to the state of the road surface 48. The brake system 18 is controlled to perform the control. For example, when it is determined that the road surface 48 is a frozen road surface, the braking control unit 44 sets the second braking distance longer than the first braking distance at the time of non-freezing in which the vehicle 1 and the target object 50 can avoid contact. The braking control is executed from the position.

  When the determination unit 38 determines that the road surface 48 is a frozen road surface, the alarm processing unit 46, for example, an alarm message such as “Road surface is frozen. And the like to execute an alarm process. The warning message or the warning light can be displayed on the display device 8 or the display device 12, for example. Further, the alarm sound can be output through the audio output device 9. Further, the warning processing unit 46 may output a warning by a message, a voice, or the like according to the degree of approach to the target object 50. When the road surface 48 is a non-freezing road surface, the warning regarding the road surface state may be omitted, and only the approach warning for the target object 50 may be output.

  The operation of the driving support device 28 configured as described above will be described with reference to the flowchart of FIG. When the power of the vehicle 1 is ON, the distance measuring unit 17 constantly transmits and receives the ultrasonic wave W to measure the presence or absence of the target object 50 around the vehicle 1 and the distance to the target object 50. And Then, by the operation of the traveling support device 28, the presence or absence of the frozen road surface is determined. In addition, the traveling support device 28 executes automatic braking control for preventing the vehicle from contacting the target object 50.

  First, the driving support device 28 constantly checks whether there is a request for starting driving support from the user using the operation input unit 10 or the like (S100). End the flow. On the other hand, when the user operates the operation input unit 10 or the like to request the start of driving support (Yes in S100), the determination unit 38 determines that the data of the reflected wave acquired by the wave reception control unit 30b is It is determined based on a plurality of conditions (e.g., first to fourth conditions) whether or not the data indicates 48 freeze. If the number of data that satisfies each condition is equal to or greater than a predetermined threshold (fifth condition), it is determined that the road surface 48 is a frozen road surface. Therefore, the determination unit 38 first initializes a freeze determination counter value temporarily stored in a storage unit such as the RAM 14c to determine whether the road surface 48 is a frozen road surface (S102). Then, the driving support device 28 refers to the control state of the brake system 18 and determines whether or not the driver has operated the brake operation unit 6 (brake pedal) or performed an avoidance operation such as automatic braking by the brake system 18 itself. Is determined (S104). When the avoidance operation has not been performed (No in S104), the information acquisition unit 32 acquires the ambient temperature of the vehicle 1 from, for example, a temperature sensor provided in the air conditioner, the distance measurement unit 17, or the like (S106).

  First, when the ambient temperature is lower than the temperature threshold value A (first condition, for example, “0 ° C.”) (Yes in S108), the determination unit 38 determines the signal of the reflected wave of the ultrasonic wave W acquired by the reception control unit 30b. It is determined whether the intensity (peak value) is equal to or greater than a predetermined value (peak value threshold B) as the second condition (S110). That is, when the ambient temperature is lower than “0 ° C.”, it is determined that the data of the received reflected wave (the plot points in FIG. 7 and the like) may be data indicating the freezing of the road surface 48 and the first condition Is satisfied. When the acquired reflected wave has a peak value equal to or higher than the peak height threshold B (when a strong reflected wave returns), the indirect wave reflected on the frozen road surface is superimposed on the reflected wave data (plot point). It is determined that there is a possibility that the second condition has been satisfied, and it is determined that the data of the reflected wave may be data indicating freezing of the road surface 48, and the second condition is satisfied. Note that the reflected wave attenuates as the propagation distance increases. In other words, even if the reflected wave indicates the possibility of freezing, the peak value of the reflected wave reflected at a position far from the distance measuring unit 17 is lower than the peak value reflected at a near position. As described above, the distance to the target object 50 causing reflection can be calculated based on the transmission / reception time of the ultrasonic wave W and the sound speed at the current temperature. Therefore, the wave height threshold value B as the second condition may be changed according to the position of the target object 50 (the object that causes the ultrasonic wave W to be reflected). In this case, for example, the relationship between the distance to the target object 50 on the frozen road surface and the peak value is created in advance as a peak value map and stored in the ROM 14b or the like, and the distance to the target object 50 is determined in the determination of S110. Accordingly, the peak value B corresponding to the distance may be read. In this case, in FIG. 7, for example, even when the reflected wave from the target object 50 at a distance of 6000 mm is low, it may be determined that the data indicates the freezing of the road surface 48, which can contribute to the improvement of the determination accuracy.

  In S110, when the peak value ≧ the peak threshold B (Yes in S110), the determination unit 38 next compares the distance to the target object 50 with the distance threshold C as a third condition (S112). As described above, when the distance from the distance measurement unit 17 to the target object 50 is short, a strong reflected wave of a predetermined value or more returns regardless of whether or not the road surface 48 is frozen. In addition, for example, when performing the braking control while performing the reverse traveling at a low speed (for example, 10 km / h or less) for parking or the like, the traveling support device 28 in the present embodiment determines in advance that the vehicle is on a frozen road surface ( Detection) and start the braking operation (contact avoidance operation) early in anticipation of an increase in the braking distance on a frozen road surface. Therefore, it is necessary to use the reflected wave from the distance measuring unit 17 from a predetermined distance or more as data to be used for determining a frozen road surface. Therefore, as a third condition, for example, the required threshold distance at low speed retreat on a frozen road surface is referred to as a distance threshold C = 3000 mm, for example. If the distance from the target object 50 ≧ the distance threshold C (3000 mm) (Yes in S112), the determination unit 38 acquires the current vehicle speed of the vehicle 1 based on the detection value of the wheel speed sensor 22 (S114). The determining unit 38 determines whether the vehicle 1 is approaching the target object 50 as a fourth condition using the acquired vehicle speed (S116). That is, when the current traveling state of the vehicle 1 is moving away from the target object 50, that is, when the vehicle 1 is traveling forward, there is no need to perform a contact avoidance operation on the target object 50, and the rear road surface of the vehicle 1 is not required. There is little need to determine the state of. Whether the vehicle 1 is approaching or moving away from the target object 50 can be determined, for example, by comparing the approach speed between the target object 50 and the vehicle 1 and the own vehicle speed of the vehicle 1. For example, when the approach speed ≧ the vehicle speed of the vehicle 1 (Yes in S116), it can be determined that the vehicle 1 is approaching the target object 50. That is, when the temperature of the reflected wave is lower than the predetermined temperature (temperature threshold A), it can be determined that the signal intensity (wave height threshold B) is equal to or higher than a predetermined distance (distance threshold C) and higher than a predetermined value. In this case, the determination unit 38 determines that the data of the reflected wave acquired by the wave reception control unit 30b is data indicating that the road surface 48 is frozen, and updates the freeze determination counter value by “+1” (S118). On the other hand, in S116, if the approach speed is not equal to or more than the own vehicle speed of the vehicle 1 (No in S116), that is, if the vehicle 1 is moving away from the target object 50, it is unnecessary to detect the frozen road surface behind the vehicle 1. A determination is made and a freeze determination counter value is initialized (S120).

  Subsequently, the determination unit 38 checks whether a predetermined period has elapsed since the initialization of the freeze determination counter value (S122). In the case of the present embodiment, as described with reference to FIG. 7 and the like, when a reflected wave having a signal strength equal to or more than a predetermined value from a predetermined distance or more is obtained for a predetermined number of times or more when the temperature is lower than a predetermined temperature, the vehicle 1 It is determined that the road surface 48 in the traveling direction is a frozen road surface. Therefore, regardless of whether or not the reflected wave can be actually received, it is necessary to collect the reflected wave for a certain period. If the predetermined period has not elapsed from the initialization of the freeze determination counter value (No in S122), the process returns to S104, and the determination unit 38 determines that the reflected wave data acquired by the wave reception control unit 30b is to freeze the road surface 48. Is determined, and the process of updating or initializing the freeze determination counter value is repeated.

  In S112, when the distance from the target object 50 is not equal to or greater than the distance threshold C (No in S112), that is, the acquired data of the reflected wave is data based on the reflected wave from a distance close to the distance measuring unit 17. Is the case. In this case, it is impossible to determine whether or not the peak value is equal to or higher than the threshold value B and a strong reflected wave is obtained even if the reflected wave is reflected on a frozen road surface. Therefore, the determination unit 38 does not perform the process regarding the freeze determination counter value, stores the data of the reflected wave in the RAM 14c, and proceeds to the process of S122. In this case, the acquired data of the reflected wave is used as data indicating the distance to the target object 50 and the like. Further, in S110, the case where the peak value ≧ the peak value threshold B is not satisfied (No in S110), that is, the case where the reflected wave is low (weak). In this case, even if the ambient temperature is lower than the temperature threshold A, the road surface 48 may be in a non-freezing state, for example, a snowy road surface. Therefore, the determination unit 38 does not perform the process regarding the freeze determination counter value, stores the data of the reflected wave in the RAM 14c, and proceeds to the process of S122. In this case, the acquired data of the reflected wave is used as data indicating the distance to the target object 50 and the like. If the ambient temperature is equal to or higher than the temperature threshold A in S108, it is highly possible that the road surface 48 is not frozen. Therefore, in this case, the determination unit 38 does not perform the process regarding the freeze determination counter value, stores the data of the reflected wave in the RAM 14c, and proceeds to the process of S122. Also in this case, the acquired data of the reflected wave is used as data indicating the distance to the target object 50 and the like. In S104, when the vehicle 1 is currently performing the avoidance operation (Yes in S104), it is determined that it is not necessary to determine the state of the road surface 48, and the determination unit 38 sets the freeze determination counter value to Initialization (S124), the process proceeds to S122. Also in this case, the acquired data of the reflected wave is used as data indicating the distance to the target object 50 and the like.

  In S122, when a predetermined period has elapsed since the initialization of the freeze determination counter value (Yes in S122), that is, when the reflected wave collection processing is completed for a certain period, it is determined whether the road surface 48 is a frozen road surface. A determination threshold D to be referred to when making a determination is determined (S126). As described above, the determination threshold D is determined by referring to the map of FIG. 10 based on the vehicle speed of the vehicle 1 acquired in S114, for example, because the number of data of the reflected waves that can be acquired varies depending on the current vehicle speed of the vehicle 1. can do. Then, in S118, the determination unit 38 compares the updated freeze determination counter value with the determination threshold D determined in S126 (S128). Then, when the freeze determination counter value ≧ the determination threshold D (Yes in S128), for example, as shown in FIG. 38 determines that the state of the road surface 48 is “frozen” (S130). Then, the alarm processing unit 46 executes an alarm process of notifying the user that the road surface 48 is a frozen road surface by using the display device 8 and the audio output device 9 (S132). On the other hand, in S128, if the freeze determination counter value is not equal to or greater than the determination threshold D (No in S128), for example, as shown in FIG. It is determined that the state of the road surface 48 is "non-freezing" (S134).

  When it is determined that the state of the road surface 48 is “freeze” (Yes in S136), the deceleration start position calculation unit 42 extends the braking distance (S138). For example, the required braking distance at the time of freezing is, for example, 1.5 times the required braking distance at the time of non-freezing at the same vehicle speed. Then, when the road surface 48 is a frozen road surface, the deceleration start position calculation unit 42 refers to the current vehicle speed of the vehicle 1 and calculates a deceleration start position at which contact with the target object 50 can be avoided and the vehicle can be stopped smoothly. (S140). In S136, when it is determined that the state of the road surface 48 is not a frozen road surface (No in S136), the process of S138 is skipped, and the braking distance on the non-freezing road surface, that is, the normal braking, is performed in the process of S140. The deceleration start position is calculated using the distance (S140).

  The braking control unit 44 refers to the distance to the target object 50 calculated by the distance calculation unit 40, and the current position of the vehicle 1 with respect to the target object 50 reaches the deceleration start position calculated by the deceleration start position calculation unit 42 (Yes in S142), the braking control is started (S144). For example, the automatic braking is started using the brake system 18. In S142, if the vehicle has not reached the deceleration start position, the driving support device 28 proceeds to the process of S104, and performs a process of acquiring a reflected wave in order to continuously determine whether or not the vehicle is on a frozen road surface. And the process regarding the freeze determination counter value is repeatedly performed.

  As described above, according to the traveling support device 28 of the present embodiment, the distance measuring unit 17 that detects the presence or absence of the target object 50 and the distance to the target object 50 is used, and the road surface 48 in the traveling direction of the vehicle 1 is used. It can be obtained (or estimated) in advance whether or not the state is a frozen state. As a result, when the road surface 48 in one traveling direction is a frozen road surface, the deceleration start position is changed to a position closer to the non-freezing road surface in consideration of slippage on the frozen road surface to avoid contact with the target object 50. It is possible to reliably perform the operation. In addition, since the braking operation can be performed with a margin, smooth deceleration and stop can be realized.

  In the above-described embodiment, an example has been described in which it is determined whether the road surface 48 in the traveling direction is a frozen road surface while the vehicle 1 is traveling backward at a low speed. In another embodiment, it is possible to determine whether the road surface 48 in the traveling direction is a frozen road surface while the vehicle 1 is traveling forward at a low speed, and the same effect can be obtained. In this case, the distance measuring units 17e to 17h provided in front of the vehicle 1 are used. When determining whether or not the road surface 48 is a frozen road surface, whether to use the distance measuring units 17a to 17d on the rear side of the vehicle 1 or the distance measuring units 17e to 17h on the front side of the vehicle 1 is determined. For example, when the driving support device 28 obtains a driving support start request, it is determined whether the vehicle is in the forward traveling state or the reverse traveling state based on the position (R position or D position) of the shift operation unit 7 that can be acquired from the shift sensor 23. It can be obtained and determined whether there is.

  In the above-described embodiment, an example is shown in which, when it is determined that the road surface 48 in the traveling direction of the vehicle 1 is a frozen road surface, the vehicle 1 is braked without contacting the target object 50 by extending the braking distance. Was. In another embodiment, the road surface μ may be acquired by using a known technique and the braking force may be adjusted while it is determined that the road surface is a frozen road surface and the braking control is actually performed. In this case, smoother braking can be realized.

  In the present embodiment, an example in which ultrasonic waves are used to determine whether or not the road surface 48 in the traveling direction of the vehicle 1 is a frozen road surface has been described. However, similar effects can be obtained by using audible sound. it can. In the present embodiment, sound waves (for example, ultrasonic waves) are used to determine whether the road surface 48 in the traveling direction of the vehicle 1 is a frozen road surface. When sound waves (for example, ultrasonic waves) are used, they are not affected by ambient brightness. Therefore, for example, even at night or in a tunnel, the determination as to whether or not the vehicle is on a frozen road surface can be performed with higher accuracy than when determining based on, for example, an image.

  The driving support program executed by the CPU 14a of the present embodiment is a file in an installable format or an executable format in a computer such as a CD-ROM, a flexible disk (FD), a CD-R, and a DVD (Digital Versatile Disk). You may comprise so that it may record and provide on the readable recording medium.

  Further, the driving support program may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Further, the driving support program executed in the present embodiment may be provided or distributed via a network such as the Internet.

  Although the embodiment and the modification of the present invention have been described, the embodiment and the modification are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 14 ... ECU, 14a ... CPU, 17 (17a-17h) ... Distance measuring part, 18 ... Brake system, 28 ... Driving assistance device, 30 ... Sound wave control part, 30a ... Wave transmission control part, 30b ... Reception Wave control unit, 32 information acquisition unit, 34 vehicle speed calculation unit, 36 threshold value determination unit, 38 determination unit, 40 distance calculation unit, 42 deceleration start position calculation unit, 44 braking control unit, 46 alarm Processing unit, 48 road surface, 50 target object, 100 driving support system.

Claims (4)

A sound wave control unit that transmits a sound wave in the traveling direction of the vehicle and acquires information on the reflected wave from a distance measuring unit that receives a reflected wave reflected from an object,
An information acquisition unit that acquires temperature information around the vehicle;
When the temperature based on the temperature information is less than a predetermined temperature, based on the information of the reflected wave, when it is determined that the distance measuring unit has received a reflected wave of a signal strength of a predetermined value or more from a predetermined distance or more, A determining unit that determines that the road surface in the traveling direction of the vehicle is a frozen road surface,
A driving support device comprising:   When it is determined that the frozen road surface, the vehicle and the object traveling toward the object existing in the traveling direction of the vehicle that reflected the sound wave can avoid contact, when the road surface is not frozen The driving support device according to claim 1, further comprising a control unit configured to execute a braking control from a position of a second braking distance longer than the first braking distance.   The driving support according to claim 1, wherein the sound wave control unit obtains information on the reflected wave from the distance measurement unit provided so as to be capable of transmitting a wave substantially in parallel with the traveling direction of the vehicle. apparatus.   The determination unit has a determination threshold value for determining that the road surface is the frozen road surface when the reception frequency of the reflected wave having the signal strength equal to or greater than the predetermined value is equal to or greater than a predetermined number of times. The driving support device according to any one of claims 1 to 3, wherein the driving support device is changed according to a speed of the vehicle at the time of the determination.

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